Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
You created a process with a restart policy, and the engine did not accept one of your words. When you call process new, you can say how the process should be restarted. The restart word is one of three: always, never, or on failure. You can also give a budget, which is a small labeled map with two labels: count, how many restarts are allowed, and within, the time window, written as timeout and a number. This time, something in your policy was not one of those. Maybe a restart word that is not in the list. Maybe a budget that is not a labeled map. Maybe an unknown label, or a within that is not written as timeout of a number. There is also the replay setting, which takes only true or false. The engine writes no policy it cannot read back, so it refuses by name. The message gives you the offending word and what is lawful instead. Replace it with one of the declared words, and your process will be born with exactly the policy you intended.
Text from the Rush engine's error catalogue.